In recent years, the number of patients with urban diseases, such as pollen allergies and house dust allergies, has been rapidly increasing. In particular, 15% to 20% of the population in Japan is said to suffer from pollen allergies. In addition, it is said that the number of such patients will increase in the future, and that this problem will become more serious. Even though symptoms of pollen allergies significantly influence patients' lives in the form of, for example, a runny nose, cough, or an itchy eye, such symptoms are not life-threatening, and many patients are thus forced to merely endure such symptoms. In addition, a variety of therapeutic techniques have been attempted in hospitals, although no definite therapeutic techniques have been found. At present, accordingly, anti-inflammatory steroids are used to alleviate severe symptoms.
Since steroids are hormones in living organisms, steroidal anti-inflammatory agents with strong anti-inflammatory effects exert physiological effects as hormones in vivo, in addition to their anti-inflammatory effects. Accordingly, strong side effects thereof have been pointed out, and use of steroids should be strictly supervised by doctors. In addition, many patients are concerned about such side effects. Unlike medicine, food with health-promoting benefits is not intended to treat diseases. However, introduction of such food into a regular diet is expected to easily realize disease prevention or symptom alleviation. Accordingly, high expectations are placed on such food as a means of realizing an improvement in patients' quality of life.
Allergic diseases, such as pollen allergies and atopic dermatitis, are referred to as type I hypersensitivity or immediate hypersensitivity in the medical field, and many researchers have been studying the pathogenic mechanisms thereof. To date, the following has been elucidated. First, pollens that are allergens inhaled by breathing bind to IgE antibodies as the immune responses in vivo. Further, pollen-IgE antibody conjugates bind to mast cells. Thus, chemicals such as histamines and leukotrienes are released from the mast cells, and such substances cause inflammations in the nose, the eyes, and the respiratory tract. That is, IgE antibodies trigger allergies against the invasion of the body by pollens. Thus, an in vivo reduction of IgE antibodies would result in the inhibition of allergy symptoms.
The present inventors had constructed an experimental system capable of reproducing IgE antibody production in vitro by conducting in vitro culture of immunocytes associated with IgE antibody production in vivo. The present inventors had independently constructed a culture system involving the use of human peripheral blood lymphocytes simulating the in vivo kinetics of human allergies and identified ingredients exerting anti-allergic effects from among food ingredients. Unlike conventional test techniques involving the use of a large number of test animals such as mice, the aforementioned technique allows the simultaneous testing of several hundred types of specimens over a culture period of about 10 days, and such technique is thus highly efficient. Because of the use of human cells, in addition, when an effective ingredient is found among the searched factors, such ingredient is highly likely to exert effects in vivo, and the time required for screening can also be shortened. Furthermore, the interaction between the screened factor and a cell may be examined so as to elucidate the action mechanism of such factor at the cellular level. Accordingly, this technique has many advantages, such that functions of food can be evaluated from a scientific perspective (Non-Patent Document 1).